The present disclosure relates to a method and apparatus for calculating a rotation angle of a device, and more particularly, to a method and apparatus for calculating an inclination angle of a device with respect to a moving direction of the device.
Pedestrian dead-reckoning (PDR) may be used for estimating a position by using devices such as smartphones. In PDR, an inclination angle of the device substantially affects position estimation performance. When the inclination angle of the device is miscalculated, an error may still be present even though a moving distance has been accurately calculated.
In particular, when a user of a small device such as a smartphone moves while gripping the device in his/her hand, an inclination angle of the device with respect to a moving direction of the device may change arbitrarily depending on user convenience or an intention of the user. For example, assuming that the user is moving while gripping the smartphone in a vertical direction (portrait mode) or a horizontal direction (landscape mode), when the user is moving while the smartphone is inclined in a yawing direction by about 60° with respect to a moving direction, it may be difficult to calculate an inclination angle of the smartphone with respect to the moving direction of the user by only using a built-in accelerometer of the smartphone. Due to inaccurate calculation, position calculation results may have many errors.
It is difficult to calculate the inclination angle of the device with respect to the moving direction of the device because an accelerometer in the device senses gravitational (gravity axis) acceleration, information about acceleration in a direction in which the user is moving, and vertical acceleration information, but cannot distinguish between the acceleration components.
According to the related art, an inclination angle of a device with respect to a moving direction of a user may be calculated by interpreting acceleration information, which is sensed by using an accelerometer, a gyroscope, and a geomagnetic sensor, in a frequency range or by using movement dynamics of the user.
When the inclination angle of the device is calculated by using a reaction acceleration vector at which the user takes a step, the inclination angle of the device with respect to the moving direction of the user may have an error because the reaction acceleration vector may not be easily distinguished due to sensor noise. Although final calculated angle information may be filtered by a low pass filter to reduce errors, calculation time may be delayed due to the filtering process.
The present disclosure provides a method of efficiently distinguishing between gravitational acceleration, vertical acceleration, and horizontal acceleration based on information sensed by only an accelerometer, by recognizing movement characteristics of the user as the user moves. By distinguishing the gravitational acceleration from acceleration information, the inclination angle of the device with respect to the moving direction of the user may be more accurately calculated compared to methods in the related art. This technology may increase position calculation accuracy of mobile phones, and perform position calculation using low power by reducing sensing power consumption.